Improved Reusable Capture Complex

ABSTRACT

The present invention is in the field of an improved reusable capture complex and a method of releasable capturing an additive present in a polymer material. The capture complex comprises a catalyst entity, a magnetic nanoparticle, and a bridging moiety solely between the catalyst entity and the magnetic nanoparticle The present use and method provide a high reduction of free additive of a polymer material.

FIELD OF THE INVENTION

The present invention is in the field of an improved reusable capturecomplex and a method of releasable capturing an additive present in apolymer material. The present use and method provide a high reduction offree additive.

BACKGROUND OF THE INVENTION

A problem with many chemical processes is interference of contaminantswith the process. Therefore these contaminants are preferably removedbefore the process starts, i.e. it is a goal to start with as pure aspossible sources. However, if the contaminants are present in one of thesource products to be processed, such as in a polymer material, removalis at least complicated and in certain cases even virtually impossible,such as in the case of additives being present in polymers. Upondegradation of such polymers in the polymer material the additives arereleased and may interfere with e.g. the degradation process and maycause side reactions to occur. In such cases the additives arepreferably removed during the degradation process, and preferably areremoved continuously.

An interference of additives considered relates to interference with acatalyst. Typically catalysts, and especially complexes, and function ofa catalyst are sensitive to contaminants being present; in other wordsthey function only properly under relative pure and clean conditions. Asa result of contamination catalysts need to be replaced regularly, andextreme care is typically taken not to introduce contaminants. That mayalso be a reason why catalyst are typically not considered fordegradation processes, such as of polymers, as these processes almostinherently introduce contaminants, e.g. in the form of additives beingpresent in the polymer material, such as curing agents, plasticizers,property modifiers, stabilizers, surfactants, fillers, colorants,pigments, antioxidants, antistatic, anti-fungi, anti-bactericides,UV-blockers, UV-stabilizers, and lubricants. These additives form aserious obstacle in finding a method for degrading polymers.

It is known to use finely divided materials, such as carbon black andnanoparticles, to remove contaminants from aqueous systems, such aswaste water. Such small materials can typically not be used innon-aqueous systems, and typically also are not compatible with polymerdegradation processes, e.g. because of interference with the process,because of inadequate mixing properties, and non-dispersibility insolvents typically used.

Therefore there still is a need for adequate removal of contaminants, inparticular in polymer degradation processes, which removal does notinterfere with the process itself.

The present invention provides an improved method of removing additivesfrom polymer materials and an additive capturer e.g. for degradingpolymers which overcomes at least one of the above disadvantages,without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to use of an improvedreusable capture complex for releasable capturing an additive present ina polymer material according to claim 1, and in a second aspect to amethod according to claim 7, showing partly major improvements over theprior art, e.g. in terms of a very low amount of complex used per amountof additive (0.2-18 wt. % versus 17-80 wt. % [weight catalyst/weightpolymer]), insensitivity to contaminants, such as environmentalsubstances, insensitivity to composition of raw material (i.e. type ofpolymer material to be degraded and type of additive), etc. Put innumbers the present invention provides a reuse of capturer (over 50times, being absent in prior art degradation processes), allowing anymixture of waste polymers (not known in the prior art, typically wellcleaned, well separated, having one type/source of material, is neededfor prior art processes), etc.

The present capture complex comprises three distinguishable elements: ananoparticle, a bridging moiety attached, such as by a covalent bond, tothe nanoparticle and a catalyst entity (chemically, such as by acovalent bond) attached to the bridging moiety. The bridging moiety issolely in between the catalyst and the nanoparticle, respectively, e.g.no “coating” or shell is present on the nanoparticle. The presentcomplex is for instance different from a complex having a bridgingmoiety fully covering a nanoparticle, such as in a core-shell particle.The complex may be an ionic complex.

The additive is typically present in a small amount, such as in amountof <10.000 ppm (based on a total amount polymer). The present capturecomplex is particularly suited for capturing colored additives, moreparticularly a dye, a pigment, an ink, a paint, and a coloured chemical.

It is noted that the capture complex is intended to perform variousfunctions, such as catalysis of polymer degradation, capturing ofadditives, etc. In view of a polymer degradation process the presentcomplex preferably does not disperse well in a water or an aqueoussolution, contrary to e.g. nanoparticles per se.

The present nanoparticle is of a magnetic or non-magnetic nature. Assuch nanoparticles comprising a magnetic material are included, as wellas particles that can be magnetized sufficiently under relative modestmagnetic fields, such as being applied in the present method. The use ofmagnetic nanoparticles has the advantage that these may for instance berecovered by magnetic attraction after use. Suitably, the magneticnanoparticles contain an oxide of iron, manganese and/or cobalt. Ironoxide, for instance but not exclusively in the form of Fe₃O₄ ispreferred. Another suitable example is CoFe₂O₄.

It has been found that the nanoparticle should be sufficiently small forthe capture complex to function as a catalyst, therewith degrading thepresent polymer into smaller units, wherein the yield of these smallerunits, and specifically the monomers thereof, is high enough forcommercial reasons. It is noted in this respect that a commercial valueof (waste) polymers to be degraded is relatively small, i.e. a costs ofdegrading should be small as well. It has also been found that thenanoparticle should be sufficiently large in order to be able to reusethe present complex by recovering the present capture complex. It iseconomically unfavourable that the capture complex would be removed witheither waste or degradation product obtained. Suitable nanoparticleshave an average diameter of 2-500 nm. It is preferred to usenanoparticles comprising iron oxide.

It is noted that the present nanoparticle is not considered to be asupport. A prior art support in general relates to much larger entities,typically in the order of mm or larger. It is noted that for the presentprocess a catalyst on a support is considered unsuited, in particular asa yield of degradation products is too low (or likewise time and/ortemperature to obtain such a yield are unfavourable). For instanceValkenberg, et al. in “Immobilisation of ionic liquids on solidsupports”, Green Chemistry, 2002 (4), pp. 88-93, shows ionic liquidsattached to solid supports, e.g. a metal oxide, such as TiO₂, SiO₂,Al₂O₃, etc. Valkenberg, in table 3 shows a comparison between an Fe-ILin unsupported status and in supported status. For anisole theconversion drops from 90% to 6.5% (or about 30% for charcoal) and form-xylene it drops from about 34% to 15% (or about 18% on charcoal). Itis found important to further optimize reaction conditions. So a supportwould typically not be considered for an ionic liquid in view ofconversion.

The present catalyst entity comprises at least two moieties. Such hasbeen found to contribute to at least some of the present advantages. Afirst relates to an aromatic moiety having a positive charge (cation). Asecond relates to a moiety, typically a salt complex, having a negativecharge (anion). Within the description the term “partly” as referring tothe catalyst entity indicates that a part of the catalyst entities ischarged, hence typically not all of the entities. The negative andpositive charge typically balance one and another. It has been foundthat the positively and negatively charged moieties have a synergisticand enhancing effect on the degradation process of the polymer in termsof conversion and selectivity, especially in view of degradingpolyesters and polyethers.

The aromatic moiety preferably comprises a heterocycle, having at leastone, preferably at least two nitrogen atoms. The aromatic moietypreferably stabilizes a positive charge. The heterocycle may have 5 or 6atoms, preferably 5 atoms. Typically the aromatic moiety carries apositive charge. If a nitrogen is present the charge is on the nitrogen.Suitable aromatic heterocycles are pyridimines, imidazoles, piperidines,pyrrolidines, pyridines, pyrazols, oxazols, triazols, thiazols,methimazols, benzotriazols, isoquinols, and viologen-type compounds(having e.g. two coupled pyridine-ring structures. Particularlypreferred is an imidazole-structure, which results in an imidazoliumion.

The negatively charged moiety may relate to a salt complex moiety,preferably a metal salt complex moiety having a two- or three-pluscharged metal ion, such as Fe³⁺, Al³⁺, Ca²⁺, and Cu²⁺, and negativelycharged counter-ions, such as halogenides, e.g. Cl⁻, F⁻, and Br⁻.Alternatively, the negatively charged moiety may be a negatively chargedanion, such as a halide.

The present catalyst entity and nanoparticle are combined by a bridgingmoiety. The bridging moiety is provided for attaching the catalystentity to the nanoparticle. The attachment typically involves a physicalor chemical bonding between a combination of the bridging moiety and thecatalyst entity on the one hand and the nanoparticle on the other hand.Particularly, a plurality of bridging moieties is attached or bonded toa surface area of the present nanoparticle. It is noted that it isimportant to maintain functionality of the catalyst complex. It is notonly important to provide suitable bridging moieties (or a combinationthereof), but also to fit a number of bridging moieties with respect toa surface area of the present magnetic nanoparticle. In this respectalso a size (diameter) of the present nanoparticle is important.

It has been found that especially a weak organic acid, silanol, silylcomprising groups, and silanol, attach well to the nanoparticle. Moreparticularly, therefore, the bridging moiety comprises a functionalgroup for bonding to the oxide of the nanoparticle and a second linkinggroup to the catalyst entity. The functional group is for instance acarboxylic acid, an alcohol, a silicic acid group, or combinationsthereof. Other acids such as organic sulphonic acids are not excluded.The linking group comprises for instance an end alkylene chain attachedto the aromatic heterocycle moiety, with the alkylene chain typicallybetween C1 and C6, for instance propylene and ethylene.

The bridging moiety is suitably provided as a reactant, in which thelinking group is functionalized for chemical reaction with the catalystentity. For instance, a suitable functionalization of the linking groupis the provision as a substituted alkyl halide. Suitable reactants forinstance include 3-propylchloride trialkoxysilane,3-propylbromide-trialkoxysilane, 2-propylchloride-trialkoxysilane,2-propylbromide-trialkoxysilane. The alkoxy-group is preferably ethoxy,though methoxy or propoxy is not excluded. It is preferred to usetrialkoxysilanes, though dialkyldialkoxysilanes andtrialkylmonoalkoxysilanes are not excluded. In the latter cases, thealkyl groups are preferably lower alkyl, such as C1-C4 alkyl. At leastone of the alkyl groups is then functionalized, for instance with ahalide, as specified above.

The said reactant is then reacted with the catalyst entity. Preferably,this reaction generates the positive charge on the aromatic moiety, moreparticularly on a nitrogen atom in the aromatic moiety. The reaction isfor instance reaction of a (substituted) alkyl halide with the nitrogencontaining aromatic moiety, resulting in a bond between the nitrogenatom and the alkyl-group. The nitrogen is therewith charged positively,and the halide negatively. The negatively charged halide may thereafterbe strengthened by addition of a Lewis acid to form a metal saltcomplex. One example is the conversion of chloride to FeCl₄ ⁻.

For performance of the process in terms of conversion, selectivity, andeconomical feasibility the above needs to be taken into account;otherwise no effective capturing of additives is obtained, therewithdeteriorating. The present bridging moiety provides the abovecharacteristics (in addition to the present nanoparticle). It is notedthat up to now no economically viable process for polymer degradationhas been provided.

In an example of the present capture complex the bridging moiety (andthe catalyst entity bonded thereto) is provided in an amount of (molebridging moiety/gr magnetic particle) 5*10⁻¹⁰-0.1, preferably1*10⁻⁷-0.01, more preferably 2*10⁻⁵-10⁻³, such as 4*10⁻⁵-10⁻⁴. It ispreferred to have a relatively large amount available in terms of e.g.effective capturing, whereas in terms of amount of catalyst and coststhereof a somewhat smaller amount is available, especially as themagnetic nanoparticles are considered as a relatively cheap part of thecapture complex. Surprisingly the present method can be performed withvery low amounts of capture complex, compared to prior art methods.

In an example of the present capture complex the nanoparticles have anaverage diameter of 2 nm-500 nm, preferably from 3 nm-100 nm, morepreferably from 4 nm-50 nm, such as from 5-10 nm. As indicated above,the particles are preferably not too large and not too small. It hasbeen found that e.g. in terms of use and recovery of capture complex arather small size of particles of 5-10 nm is optimal. It is noted thatthe term “size” relates to an average diameter of particles, wherein anactual diameter of a particle may vary somewhat due to characteristicsthereof. In addition the size is determined per individual particle. Foran average a number weight average may be taken. In an approximation theaverage may be taken as the size with the highest number of particles oras a median size.

In an alternative embodiment, the nanoparticles may have sizes in arange of 50-200 nm, such as 80-150 nm, e.g. 100 nm. In this embodiment,the nanoparticles are present in the form of aggregates which may beformed e.g. in the solution. These aggregates typically have sizes in arange of 50-200 nm, such as 80-150 nm, e.g. 100 nm. Particle sizes and adistribution thereof can be measured e.g. by light scattering, e.g.using a Malvern Dynamic light Scattering apparatus, such as a NS500series. In a more laborious way, typically applied for smaller particlesizes and equally well applicable to large sizes representativeEM-pictures are taken and the sizes of individual particles are measuredon the picture.

In case of degradation the solid polymer is provided in a suitablesolvent. As such the method may be considered as a solid-liquiddegradation process supported by addition of a recoverable capturecomplex. For instance, alcohols may be used. Preferred alcohols arealiphatic, for instance alkanols and alkanediols. Mixtures of alcoholsand/or mixtures of water and alcohols are also deemed feasible. For aglycolysis the solvent is preferably a mono- or di-alcohol, such as analkanol or alkanediol. As such the solvent also functions as a reactantin the polymer degradation.

The method may be carried out batch-wise, continuous, semi-continuous,and combinations thereof.

Various details of the degradation method may be found in theInternational Applications PCT/NL2014/050418, and WO 2014/142661 A2,filed by the same applicant, which contents are incorporated byreference.

Suitably, the polymer to be degraded is a condensation polymer, forinstance chosen from polyesters, polyethers, polycarbonates, polyimidesand polyamides. Representative examples include PET(polyethyleneterephthalate), PEF (polyethylenefuranoate), PTT(polytrimethyleneterephthalate, PLA (polylactic acid).

It is an advantage of the present method that the method is relativelyinsensitive to contaminants, like additives, such as pigments, fillers,and filters, are separated in the course of the degradation process. Itis understood by the inventors, that the additives adhere to the capturecomplex. Particularly, the bridging moieties and catalyst entitiesjointly adhered to the nanoparticles appear to enable adsorption ofhydrophobic colorants. After the degradation process, the capturecomplex may be regenerated, in that the additives are removed bywashing. It was found in preliminary investigations that degradationtreatments of several (5-20) batches of polyester bottles may be carriedout before a washing step is needed. As such the present method isconsidered robust, to be used under relatively sub-optimal conditions,such as in a plant.

Compared to prior art methods a characteristic of the present method isthat the capture complex can be recovered. It is preferred to use thepresent capture complex in the present method. In one embodiment, therecovery comprises the steps of providing a second solvent, e.g.functioning as washing agent, and separating the capture complex fromany additives and/or the—first—solvent, for instance using anelectromagnetic field. Such separation and recovery is particularlydesired in order to separate the additives from the capture complex.Therewith the capture complex can be reused. In a further embodiment,the capture complex is re-used in the process without recovery. Ratherthe recovery occurs only after a plurality of degradation stages.

Thereby the present invention provides a solution to at least one of theabove mentioned problems. The various examples and embodiments of thepresent invention may be combined.

Advantages of the present description are detailed throughout thedescription.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a capture complex anduse thereof according to claim 1.

In an example of the present capture complex the nanoparticles are atleast one of ferromagnetic particles, anti-ferromagnetic particles,ferrimagnetic particles, synthetic magnetic particles, paramagneticparticles, superparamagnetic particles, such as particles comprising atleast one of Fe, Co, Ni, Gd, Dy, Mn, Nd, Sm, and preferably at least oneof O, B, C, N, such as iron oxide, such as ferrite, such as magnetite,hematite, and maghemite. In view of capturing capability magnetite andmaghemite are preferred magnetic particles. In view of costs, even whenfully or largely recovering the present capture complex, relativelycheap particles are preferred, such as particles comprising Fe. Inaddition non-magnetic nanoparticles could be used, typically oxidecomprising particles, such as Al₂O₃, CaO, and clays, such as T-O-T claysand T-O clays. Preferably, the nanoparticles are selected so as to besubstantially insoluble in the (alcoholic) solvents, also at highertemperatures of more than 100° C. One oxide that tends to dissolve athigher temperatures in an alcohol such as glycol, is for instance(amorphous) SiO₂. It is noted that some sophisticated tailoring may berequired.

In an example of the present capture complex the bridging moietycomprises a functional group for adhesion or bonding to the nanoparticleand a linking group towards the catalyst entity, and particularly thehetero atom of the aromatic moiety. Suitable functional groups are forinstance weak organic acid (such as a carboxylic acid or a dicarboxylicacid) and silanols, including silanediols and silanetriols. The linkinggroup is for instance an alkyl, such as ethyl, propyl, butyl, pentyl,and hexyl. When forming the present complex he bridging moiety may beintroduced as a reactant in the form of a silyl comprising group, suchas silylethers, such as triethoxysilylpropylhalide (such astriethoxysilylpropyl-3-chloride. For a weak organic acid the Katypically varies between 1.8×10⁻¹⁶ and 55.5. It has been found thatdespite negative expectations these bridging groups do not result in anon-acceptable reduced performance, such as a decreasing catalyticperformance of the catalyst entity.

In an example of the present capture complex the aromatic moiety has atleast one tail. The present tail relates to a tail like moiety. The atleast one tail preferably having a length of C₁-C₆, such as C₂-C₄, theat least one tail being attached to the at least one nitrogen atom. Ithas been found that for an optimal degradation of a polymer a somewhathigher yield is obtained when the present tail is somewhat longer. Interms of mass of capture complex provided it has been found that asomewhat shorter tail is preferred, and also in view of capturingadditives too long tails limit capturing.

In an example of the present capture complex the magnetic nanoparticlecomprises (per particle) at least one bridging moiety and catalystentity, preferably 2-10⁴ bridging moieties and catalyst entities (BC perparticle), more preferably 10-10³ bridging moieties and catalystentities (BC per particle). In principle as many catalyst entities aspossible may be provided. However the amount of catalyst entities andthere functioning is somewhat smaller than an amount that could beachieved. Also when a larger particle is selected somewhat more catalystentities may be present.

In an example of the present capture complex the amount of bridgingmoiety and catalyst (entity) attached thereto is 0.03-99 wt. %,preferably 0.1-75 wt. %, more preferably 0.2-25 wt. %, even morepreferably 0.3-10 wt. %, relative to a total weight of capture complex.Likewise as above, a relative low amount of 0.1-5 wt. % of catalystentity has been found to be optimal, such as 0.6-3 wt. %, within furtherboundary conditions such as applied temperature. An amount of catalystand/or bridging moiety may be determined by TGA. It is noted that thepresent catalyst and bridging moiety may form a single (mono-) layer, ora part thereof not fully covering the nanoparticle. Before applying thepresent capture complex in the present method it may be washed. Theabove weight percentages are relative to a total weight of (dry) capturecomplex.

In a second aspect the present invention relates to a method accordingto claim 7. Therein an additive is provided, typically being releasedfrom a polymer upon degradation thereof. It has been found that thepresent method and capture complex are also suited in methods whereinnatural polymers are degraded. The additive is preferably captured underaddition of an excess (in terms of capability of capturing) presentcapture complex. The excess is determined on a molar basis. The additiveis typically hydrophobic of nature.

In an example of the present method the additive and complex are presentin a hydrophilic solution, such as ethylene glycol and water. The methodmay further comprise the steps of precipitating the complex andadditive, such as by decreasing a temperature; removing the hydrophilicsolution, such as by decanting; adding a washing agent, such as CH₂Cl₂;dissolving the additive in the washing agent, and recovering thecomplex. As an alternative to precipitation the capture complex may befiltered. With this relative simple method most or virtually all of theadditive can be captured and released from the capture complex.

In an example, relating to pigments in depolymerized PET (monomer/BHET),no remaining pigment could be detected, such as by ¹H NMR.

In an example the present method further comprises the step of adding ahydrophilic solution when adding the washing agent, i.e. an organicsolvent that is preferably a hydrophobic solvent. Therewith a two-phasesystem is created. As such the hydrophobic additive is separated frome.g. a reaction product.

In an example of the present method a polymer provides the additive upondegradation, wherein the polymer is a mixture of waste polymers, themixture optionally comprising at least one of coloured polymers. Withthe present method most additives can be captured, and in particularcolorants. The capturing process is very effective as no remainingadditives could be detected e.g. visually; for instance a fully clear(not coloured) solution or monomer/dimer product was obtained. UsingUV-Vis absorption of specific wavelength disappeared largely.

So the present method is capable of handling waste polymers, and evenfurther a mixture of polymers, e.g. having different characteristics,such as a different colour. The yield of degradation and capturingefficiency has been found not to be influenced noticeably. In a furtherstep an active compound, such as carbon black, may be added to captureand remove remaining additives.

It is noted that prior art methods at the most can only handlerelatively pure waste polymer, and even then results are discouraging.

In an example of the present method the polymer may selected fromnatural polymers, biobased polymers, biodegradable polymers, polymersformed (directly or indirectly) from fossil fuels, and combinationsthereof. In an example the polymer is at least one of a polyester, apolyether, such as poly-oxymethylene (POM), polyethylene glycol (PEG),polypropylene glycol (PPG), polytetramethyleneglycol (PTMG),polyethylene oxide (POE), polypropylene oxide (PPO), polytetrahydrofuran(PTHF), and polytetramethyleneetherglycol (PTMEG), a polypeptide, apolyamide, a polyamine, a polycondensate, preferably a polyester, suchas poly carboxylic ester, wherein the poly carboxylic ester ispreferably selected from polyethylene terephthalate (PET), polyethylenefuranoate (PEF), polybutylene terephthalate (PBT), polytrimethyleneterephthalate (PTT), polyglycolic acid (PGA), polylactic acid (PLA),polycaprolactone (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate(PHA), polyhydroxybutyrate (PHB), polyethylene naphthalate (PEN),Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and apolycondensate of 4-hydroxybenzoic acid and6-hydroxynaphthalene-2-carboxylic acid (VECTRAN). In other words a largevariety of polymers may be degraded by the present method. Someadjustments may be necessary, e.g. in terms of catalyst used,temperature applied, solvent used, etc. The present method is bestsuited for degradation using hydrolysis or glycolysis, such as indegradation of polyesters and polyethers, in particular PET and PEF.

After degradation the obtained mixture may be cooled down, e.g. to50-85° C. At this temperature a magnetic separation may be performed.Likewise alternative separation techniques, such as filtering,centrifugation, etc. may be used. Thereafter a mixture may be cooleddown even further, e.g. to 1-10° C., in order to precipitate e.g. amonomer or dimer. The obtained precipitate may further be dried, e.g. at50-75° C.

In an example of the present method the amount of catalyst complex is0.1-35 wt. %, preferably 0.5-20 wt. %, more preferably 1-10 wt. %, evenmore preferably 2-7 wt. %, relative to a total weight of polymerprovided, such as (weight to weight) 1 ABC:15PET (:45 EG, ethyleneglycol). If the amount of catalyst is higher a shorter reaction time wasobtained, whereas at a lower amount longer reaction times were obtained.Depending on further boundary conditions one may vary the amount ofcatalyst.

In an example of the present method the additive has an average size of1-100 nm, and a molecular weight of 10-5000 Dalton. In particular thefollowing additives can be captured. Organic based pigments, such asacridine dyes, anthraquinone dyes, arylmethane dyes, diarylmethane dyes,triarylmethane dyes, azo-dyes, diazonium dyes, nitro dyes, nitroso dyes,phthalocyanine dyes, quinone-imine dyes, azin dyes, eurhodin dyes,safranin dyes, indamins, indophenol dyes, oxazin dyes, oxazone dyes,thiazine dyes, thiazole dyes, xanthene dyes, fluorene dyes, pyronindyes, fluorone dyes, rhodamine dyes, and derivatives thereof, biologicalpigments, such as alizarin, alizarin crimson, gamboge, cochineal red,rose madder, indigo, Indian yellow, and Tyrian purple, andnon-biological organic pigments, such as quinacridone, magenta, phthalogreen, phthalo blue, pigment red 170, diarylide yellow, metal-basedpigments, such as cadmium pigments, chromium pigments, cobalt pigments,copper pigments, iron oxide pigments, lead pigments, manganese pigments,mercury pigments, titanium pigments, and zinc pigments, and furtherinorganic pigments, such as carbon pigments, clay earth pigments, andultramarine pigments, and salts thereof, and combinations thereof. Thecapture efficiency may vary, depending on the nature of e.g. thepigment, from 25% to >99.99%. In addition freed additives may becaptured by other compounds, such as carbon black.

In an example of the present method further comprises the step ofrecovering the catalyst attached to the magnetic particle using anelectro-magnetic field gradient, preferably in a magnetic field of 0.1-5T, preferably from 0.3-2 T, more preferably from 0.5-1.5 T, such as0.8-1.3 T, e.g. 1 T. As such a relatively small magnetic field is foundto be sufficient to recover the present capture complex. In view of e.g.reactor design such is advantageous. In an example water is provided, inorder to separate the present complex from the present solvent. It hasbeen found that it is much easier to remove the present complex from awater phase, than from the present solvent phase. By providing a suitedcapture complex, such as the present complex, the catalyst (complex) maybe recovered. It has been found that typically 95% of the capturecomplex can be recovered, and often even 98-99%. As a consequence thepresent capture complex can be reused 20-100 times, thereby e.g. savingcosts. It has been found that a recovered capture complex functionsequally well compared to a fresh (non-used) complex.

In an example of the present method further comprises the step ofrecycling the capture complex. After recovery the present complex can berecycled or removed and e.g. stored for later use.

In an example of the present method the polymer is polyethyleneterephthalate (PET) or PEF, the solvent is ethanediol, the catalystcomprises butylimidazole or butylmethylimidazole and FeCl₄ ⁻, thebridging moiety is triethoxysilylpropyl or trihydroxysilylpropyl, andthe nanoparticle is magnetite and/or maghemite. The nanoparticlespreferably have a size of 5-10 nm. The bridging moiety preferably ispresent in an amount of 10⁻⁴-10² mole bridging moiety/gr nanoparticle,such as 2*10⁻⁴-10⁻³. It is assumed that if a predetermined amount(moles) of bridging moiety is attached to a predetermined amount (gr)practically all of the bridging moieties attach to the nanoparticle andsubstantially stay attached during the present method. Such isespecially a preferred embodiment in view of the abundant amount ofwaste PET being available, being in excess of hundreds of thousand tonsper year.

The present capture complex may for instance be used in a ratio (weightto weight) of Complex:PET in a range of 1:5 to 1:500, such as 1:10-1:15.In addition the amount of e.g. ethylene glycol:PET may vary from 1:2 to1:20, such as 1:3 to 1:5. The waste polymers may relate to a single typeof polymer, such as PET, PEF, PA, etc., and also to a mixture thereof.It typically comprises 50-99.9 wt. % of a specific polymer, such as PET,the remainder being impurities, other polymers, other compounds, etc.

The invention is further detailed by the accompanying figures andexamples, which are exemplary and explanatory of nature and are notlimiting the scope of the invention. To the person skilled in the art itmay be clear that many variants, being obvious or not, may beconceivable falling within the scope of protection, defined by thepresent claims.

SUMMARY OF FIGURES

FIG. 1a-e shows chemical reactions and capture complexes.

DETAILED DESCRIPTION OF FIGURES

FIG. 1a shows chemical reactions. Therein poly(ethylene terephthalate)is degraded in 1,2-ethanediol. Similar results have been obtained withthe capture complex of the present invention; in an example bim is usedas aromatic catalyst entity. As a result Terephthalic AcidBis(2-Hydroxyethyl) ester (BHET) is formed. Further, it is shown thatBHET can be converted into dimers and oligomers (typically having 3-12monomers).

FIG. 1b shows a schematic representation of the present capture complex.Therein A represents a nanoparticle, such as maghemite, B a bridgingmoiety directly attached to the nanoparticle, such as trisilanolpropyl,and C a catalyst entity, directly attached to the bridging moiety, withC1 being a positive catalyst moiety, such as bim, and C2 being anegative catalyst moiety, such as Cl⁻. If present (hence not shown) atail would extent away from the nanoparticle.

FIG. 1c shows a nanoparticle A surrounded by a number of bridgingmoieties and catalyst entities and attached to the nanoparticle.

FIG. 1d shows an example of making one embodiment of the capture complexof the invention. In a first step 3-chloropropyltriethoxysilane isreacted over night with 1-butyl-imidazole under heating forming a BCsub-complex; herein the butyl forms a tail. A temperature is from320-360° K, and depending on the temperature a reaction time is from30-360 minutes. The reaction yields almost 100% BC sub-complex. The BCsub-complex is thereafter grafted on an iron oxide comprisingnanoparticle. In this example, due to the presence of the carboxylicacid group, the grafted is understood to result in adhesion.Alternatively, in the presence of a silanol group, the grafting may bein the form of chemical bonding.

FIGS. 1d and 1e show reaction equations for formation of the capturecomplex of the invention in accordance with one preferred embodiment. Ina first step (FIG. 1d ) 3-chloropropyltriethoxysilane is reacted overnight with 1-butyl-imidazole under heating forming a BC sub-complex;herein the butyl may be referred to as a tail. A temperature is from320-470 K, and depending on the temperature a reaction time is from 30min. to overnight. The reaction yields almost 100% BC sub-complex. Theresulting intermediate is the combination of positively chargedN-[3-(triethoxysilyl)propyl]-butylimidazolium and negatively chargedchloride. Subsequently, a Lewis acid, such as FeCl₃ may be added.However, that is not deemed necessary. In a second step, shown in FIG.1e , the ethoxy-groups of the said reaction product thereof areconverted to hydroxyl-groups, to result in a silanol-group. In a thirdstep, that is for instance carried out in water or in ethanol or aqueousethanol, the silanol is reacted with the nanoparticle surface,preferably in the presence of an acid. The resulting capture complex maythereafter be (re)dispersed in the desired solvent for the polymerdegradation, for instance glycol.

EXAMPLES

Tests have been performed on coloured PET and previously fornon-coloured PET. The results thereof are in the same order of magnitudefor both conversion and selectivity towards BHET. As a consequenceinventors conclude that a colour additive has hardly any or no impact inthis respect. Even further, additives, such as pigments, can be removedfrom the degradation products, with ease.

Similar tests as above have been performed on a wide range of raw (PET)material, e.g. polyester clothing, PET carpet, PET material fromautomotive industry, recycled PET, multi-layered PET trays containingother polymers, such as PE and PP. The results thereof are in the sameorder of magnitude. As a consequence inventors conclude that the processis highly insensitive to different raw (PET) material and robust aswell.

In an example inventors used 1 g of capture complex of FIG. 1e and 5 gof PET. Experiments showed that all colorants were removed by thecomplex, that is no colour was detectable in the obtained BHET/ethyleneglycol (EG)/water phase.

It has been found that the present complex is capable of removing atleast 2.5 mg colorant/g complex in one single use; examples show aremoval of 25 mg colorant/g complex in a single run. When used insequence of e.g. five times it has been found that the complex removesat least 12.5 mg colorant/g complex. When used for a large number ofsequences (e.g. up to 50 times) there is been found no drawback inefficiency; hence the complex is considered to be capable of removing atleast 125 mg/g complex. Such a capability is considered enough for mostapplications considered.

In one preferred embodiment, a washing step is per-formed in order toremove the captured compound. Advantageously, this washing needs only tobe done after a series of runs or cycles If an amount of additive islarge relative to the amount of capture complex the capture complex maybe washed; typically the capacity for capturing additives by thecomplex, as indicated above is relatively large and the complex onlyneeds to be washed after 5-10 cycles.

Further Examples

Examples Found of Degradable Polymers:

Polyesters: PET, PEF, PTT, PLA, polycarbonate

Polyethers: cellulosis

Polyamides: nylon 6

Ionic Liquids Tested:

An imidazolium based functional acid a piperidinium based functionalacid, a pyridinium based functional acid, a pyrrolidinium basedfunctional acid, a sulfonium based functional acid with an additionalside group R3, an ammonium based functional acid with additional sidegroups R3 and R4, and a phosphonium based functional acid withadditional side groups R3 and R4; all with at least side groups R1 andR2 and counter ion X—. X may be selected from F, Cl, Br, I, dicyanamide,bis(trifluoromethylsulphonyl)imide, preferably Cl.

The functional group R1 may be a (mono or multi, 1-4) carboxylic acid,whereas functional group R2 may be an alkane, typically a straight orbranched alkane. Functional groups R3 and R4 may be selected from H, CH₃and R1 and R2. Functional groups R1-R4 have been selected independentlyand may be (partly) the same, or not. The side group R2 may have m or ocarbon atoms may be branched, whereas the side group R1 having n(typically 4-20) carbon atoms is preferably unbranched.

So in summary aromatic and non-aromatic moieties had and have beentested, typically comprising a heteroatom (N, S, P), having a positivecharge on the (or one of) hetero atom(s), and various side groups havebeen tested. The most promising have been claimed, namely the aromaticones with a nitrogen atom.

Metal Salts:

Various metal salt comprising two- or three-plus charged metal ion andnegatively charged counter-ions have been tested, especially Fe, Ca, Co,Mn, and the above counter ions.

Bridging Moiety:

For the bridging moiety weak and functionalize acids have been tested,such as a carboxylic acids and an oxysilane, such as methoxysilane orethoxysilane.

Nanoparticles:

Various nanoparticles have been tested such as having O as counter ion,and Fe, Co and Mn as metal ion, and some combinations thereof. Thesefunction fine.

A size is typically relatively small, hence nanoparticles, with a lowervalue of 2 nm, and an upper value of 500 nm. Both have certain minoradvantages and disadvantages.

Recovering Catalyst:

Most or all of the catalyst can be recovered easily, depending on themethod of recovery. After 30 times recovery the amount recovered usingmagnetic recovery is higher than 98% of the initial amount, so virtuallyno losses. If filtration is used even higher amounts can be recovered.

Example 2: Depolymerisation Method

The reference scale of a laboratory experiment is 50 g of ethyleneglycol (EG) in a 100 mL flask. The reference mass ratio of the reactionis 1 g of dry catalyst complex particles: 5 g of PET: 50 g of EG. Thereference capture complex comprises 5 nm magnetite nanoparticles,trisilanolpropyl as bridging moiety and as ionic liquid (bim)FeCl₄ or(bmim)FeCl₄). A reference reaction was executed as follows:

The catalyst complex dispersion was homogenised by shaking for 5 minutesby hand. To 10 g of capture complex dispersion 41 g of EG was added andthe liquids were shortly mixed by hand to homogenise the dispersion.Then, 5 g of PET flakes were added and the round bottom flask was placedin the heating set up. The PET flakes were prepared from colored PETbottles commercially available from SPA®, as SPA® Reine (Blue in bluecolored PET bottles) and SPA® Sparkling (Red in red colored PETbottles). The heating was started and after 20 minutes, the reactionmixture had reached the reaction temperature of 150-200° C. The reactionwas followed in time by taking in-process-control samples to measure theconcentration of BHET produced as a function of time. The concentrationof BHET was determined with HPLC. The results are listed in Table 1. Itwas found that the reaction conditions (temperature, concentration ofcapture complex, type and size of nanoparticle) could be varied insufficient broad ranges.

TABLE 1 Conversion of PET to BHET as a function of time for a referencePET depolymerisation reaction Time PET to BHET conversion [min] [%] 51.7 10 5.4 15 10.0 20 10.5 35 31.8 45 51.5 60 92.4

Example 3

After the depolymerisation reaction, water was added in a 1:1 ratio andthe capture complex was separated from the liquid stream containing themonomer by magnetic separation. The liquid phase was decanted, leavingthe capture complex as a slurry-like layer on the bottom of the beaker.The capture complex could be easily redispersed with ethylene glycol. Torelease the colorants from the capture complex, an organic solvent, inthis example CH2Cl2 was added and stirred vigorously. The capturecomplex was magnetically sedimented leaving a clear red or bluesupernatant, dependent on the type of bottle used for the flakes. Thesupernatant could be decanted and the capture complex could beredispersed in ethylene glycol again.

Example 4

Examples 2 and 3 were repeated using a white PET bottles, that containedwhite-colored pigment, apparently TiO₂. However, when the magneticsedimentation was performed in the presence of the organic solvent torelease the pigment, the liquid phase was left with the sedimentedcapture complex. This was left to stand overnight and a white layer ofpigment particles had sedimented overnight on top of the capture complexsediment.

Example 5: Preparation of a Catalyst Capture Complex Preparation of theLinker-Catalyst Complex (Bridge-Catalyst)

An alkyl imidazole is mixed with a halogensilane in a 1:1 molar ratioand stirred at a slightly elevated temperatures for 8 hours.

Preparation of the Catalyst Complex

The nanoparticles are prepared based on the method first described byMassart et al. in 1981:

An Fe(II) solution is mixed with a Fe(III) solution in a 1:2 molar ratiorespectively. The iron oxide nanoparticles are formed by aco-precipitation reaction in basic medium while stirring. Subsequently,the resulting iron oxide particles are washed water and ethanol.

Next, an adequate amount of linker-catalyst complex diluted with ethanolis mixed well with the dispersion of iron oxide particles, after whichammonia added. The reaction mixture is stirred for 15 hours. Dependingon a ratio between linker-catalyst and nanoparticle an amount oflinker-catalyst per nanoparticle may vary.

The particles are washed with acetone prior to redispersion in ethyleneglycol.

The invention although described in detailed explanatory context may bebest understood in conjunction with the accompanying examples andfigures.

It should be appreciated that for commercial application it may bepreferable to use at least one variations of the present system, whichwould similar be to the ones disclosed in the present application andare within the spirit of the invention.

1. Use of an improved reusable capture complex for releasable capturingan additive in a polymer material to be degraded, the capture complexnot being dispersible in water and comprising a catalyst entity, amagnetic or non-magnetic nanoparticle, and a bridging moiety solelybetween the catalyst entity and the magnetic nanoparticle, wherein thecatalyst entity and bridging moiety are attached by a chemical covalentbond and wherein the bridging moiety and nanoparticle are attached by acovalent bond, wherein the catalyst entity comprises an aromaticheterocyclic moiety carrying a positive charge, and a negatively chargedmoiety, wherein the negative charge is on a metal salt complex moietyhaving a two- or three-plus charged metal ion or a negatively chargedcounter-ion, wherein the nanoparticles have an average diameter of 2nm-500 nm, and wherein the bridging moiety is present in an amount of5*10⁻¹⁰-0.1 Mole bridging moiety/gr nanoparticle.
 2. Use according toclaim 1, wherein the bridging moiety comprises one or more of a weakorganic acid, silyl comprising groups, and silanol.
 3. Use according toclaim 1, wherein the magnetic particles are at least one offerromagnetic particles, anti-ferromagnetic particles, ferrimagneticparticles, synthetic magnetic particles, para-magnetic particles,superparamagnetic particles, wherein the magnetic particles preferablycomprise iron oxide, or wherein the nanoparticles comprise a metaloxide.
 4. Use according to claim 1, wherein the aromatic heterocyclemoiety has at least one nitrogen atom to which a linking group of thebridging moiety is bonded.
 5. Use according to claim 1, wherein thenanoparticle comprises at least one bridging moiety and catalyst entity.6. Use according to claim 1, wherein the aromatic moiety is an aromaticheterocycle with at least one nitrogen atom, wherein the anion is anFe3+ comprising salt complex moiety, wherein the nanoparticles are atleast one of ferrite, magnetite, hematite, and maghemite, and whereinthe nanoparticles have an average diameter from 3 nm-100 nm.
 7. Useaccording to claim 1, wherein the polymer is one or more of a polyester,a polyamide, a polyamine, a polycondensate, and a polyether.
 8. Methodof capturing an additive releasable from a material, wherein the polymeris one or more of a pol-a polyamide, a polyamine, a polycondensate, anda polyether, comprising the steps of providing the additive, andcapturing the additive under addition of an excess of the complex ofclaim
 1. 9. Method according to claim 8, wherein the additive andcomplex are present in a hydrophilic solution, preferably an alkanol oralkanediol, and further comprising the steps of precipitating thecomplex and additive, removing the hydrophilic solution, adding awashing agent, dissolving the additive in the washing agent, andrecovering the complex.
 10. Method according to claim 9, wherein thewashing agent comprises a hydrophobic solvent.
 11. Method according toclaim 8, wherein a polymer provides the additive upon degradation, andwherein the polymer is a mixture of waste polymers.
 12. Method accordingto claim 11, wherein the polymer is a polyester.
 13. Method according toclaim 8, wherein the additive has an average size of 1-100 nm, and amolecular weight of 10-5000 Dalton.
 14. Method according to claim 8,wherein the polymer is polyethylene terephthalate (PET) or polyethylenefuranoate (PEF), the hydrophilic solvent is ethanediol, the catalystcomprises imidazolium, and FeCl₄ ⁻ or Cl⁻ the bridging moiety istriethoxysilylpropyl or trihydroxysilylpropyl, and the nanoparticle isat least one of magnetite, hematite, and maghemite.
 15. Method accordingto claim 8, wherein the capture complex is washed after 5-10 cycles. 16.Method according to claim 8, wherein the additive has an average size of1-100 nm and a molecular weight of 10-5000 Dalton.
 17. Method accordingto claim 8, wherein at least one additive is an organic pigment. 18.Method according to claim 8, wherein at least one additive is ametal-based pigment.
 19. Method according to claim 18, wherein theadditive is a TiO₂ pigment.
 20. Method according to claim 12, whereinthe polyester is a waste material from polyester bottles.